1. Field of the Invention
This invention relates to lead bonding machines for semi-conductor devices. More particularly, this invention relates to machines for gang bonding integrated circuit devices to the flexible conductive leads of a conductive foil pattern carried on a sprocketed lead frame tape. Machines of the type disclosed herein have been referred to as gang lead bonders, inner lead bonders, outer lead bonders and flexible lead bonders.
Bonding machines of the type described herein are provided with reels of flexible lead frame tape having micro etched patterns wherein the etched patterns have conductive fingers arranged so that the ends of the conductive fingers will match the pattern of terminals on the integrated circuit chips or on the substrate to which the fingers are to be bonded.
2. Description of the Prior Art
The trend in the manufacture of semiconductor devices is to make larger and more complex integrated circuit devices. The number of active devices per unit of area base material is being increased which aids in making the individual active devices faster and cheaper. The internal connections between components and active devices in such semiconductor devices are made during the process of producing the integrated circuit chip.
The single most time consuming assembly operation in the manufacture and packaging of semiconductor devices is the wire bonding or lead attaching operation wherein conductive wires or prefabricated leads are attached to the terminals of an integrated chip and the other end of each of the wires or prefabricated leads is connected to a substrate or supporting carrier assembly.
Heretofore, it has been common practice to wire bond one terminal at a time with metal conductive wires employing manually operated wire bonding machines.
Beam lead bonding machines have been made for bonding expensive specially designed integrated circuit chips to substrates. Beam lead bonding chips are provided with cantilever leads which extend outward from the chip. The extended leads on the chip may be superimposed over a pattern on a substrate and the gold beam leads are thermal compressions bonded to the substrate. Heretofore it has been almost impossible to maintain the face of the bonding tool coplanar with the terminals or the substrate so as to maintain uniformly the pressure on each of the beam leads while attempting to simultaneously bond the beam leads to the substrate. To overcome the problem of non uniform bonding pressure such techniques as compliant bonding and the use of wobble bonding tools have been employed. Gang bonding of beam lead devices is difficult to maintain in production, is expensive and by the nature of the device reduces the yields of chips per wafer and requires a slow bonding process.
Before beam lead integrated circuit devices were popular, solder flip-chip integrated circuits were bonded to substrates. This technique creates problems in aligning the solder bumps on the integrated circuit with the conductors or pads on the substrate. Further, solder flip-chip devices are not usable in processes which require reheating the substrate or the flip-chip device above the solder temperature.
To overcome the above and other problems, flexible lead frame tapes have been employed. The flexible conductor leads or fingers carried on the lead frame tapes have been bonded to the terminals of integrated circuit chips. Flexible lead bonders have made it easier to align the bonding tool surface with the surface of the integrated circuit device and by employing solder eutectics and/or collapsible metal bumps on the integrated circuit devices have eliminated the need for exact coplanar alignment.
Heretofore, it has been necessary to manually adjust the final relationship or position of the integrated circuit terminals to the fingers or leads on the pattern of the lead frame carrier because the lead frame patterns being bonded to the integrated circuit device are not precisely located relative to the sprocketed holes used for locating the pattern. Further, the indexing mechanisms of the bonding machines heretofore employed to advance and locate the lead frame tape frame pattern have introduced errors which had to be compensated for by manual adjustment. These and other problems to be discussed herein after have prevented the best utilization of accurate automatic indexing tables. Such automatic indexing tables are capable of holding and advancing the integrated circuit chips on an anvil opposite the lead frame patterns more accurately than has been heretofore possible to locate the lead frame pattern relative to the bonding tool.